Method for predicting point of projectile impact



March 1955 D. F. c. REEVES 2,702,945

METHOD FOR PREDICTING POINT OF PROJECTILE IMPACT Filed Aug. 24, 1951 Q & a

wv wn Via United States Patent METHOD FOR PREDICTING POINT OF PROJECTILE IMPACT Daniel F. C. Reeves, Madison, Tenn. Application August 24, 1951, Serlal No. 243,412 3 Claims. (CI. 33-46) .This invention relates to a method for predicting center of impact of "projectiles to be fired from projectilelaunching apparatus, and, by extension, to a method of calibrating or adjusting conventional aiming sights by the-use of said first-mentioned method.

More specifically the invention contemplates employ ing a bore-sighting or other sighting means invariably alinable with the bore of a gun or rocket-launcher, etc., preferably a telescopic optical sighting device designed either for partial or complete insertionin the muzzle or the breech of a gun or the like; and further contemplates calibrating said device by the method hereinafter disclosed, so that it may be used at any time to accurately predict center of impact of projectiles fired therefrom, without the necessity of additional test-rounds. Conventional sighting apparatus thus can be alined or zeroed-in without the dangerous (location-revealing), costly and time-consuming test-firing method heretofore employed.

Prior to this invention, when a conventional aimingsight was removed, replaced, damaged or otherwise disturbed, so as to cast doubt upon its accurate alinement with the bore of the gun, it Was necessary to fire a projectile (or preferably a series of three or more rounds) to establish a center of impact upon which the'conventional sight was fixed. This procedure was not only costly in the economic sense, but sometimes seriously depleted the supplyof ammunition in actual combat. This invention makes possible the establishment or prediction of the point of impact without the expenditure of valuable ammunition, thus permitting quick, convenient and economical alining of conventional aiming sights. And of much greater importance, this invention makes possible hits with the first shot, a very great tactical achievement and advantage in actual combat.

Objects of the invention It is accordingly an object of the invention to provide a method of predicting the center of impact of projectiles to be fired from a certain gun, or group of identical guns, or the like, to make possible hits on the first shot and to save the expenditure of ammunition heretofore test-fired for the same purpose.

It is a further object to provide a method of adjusting conventional sighting devices by the use of my method for predicting the center of impact.

These and other objects and advantages of the invention will become apparent as the description proceeds.

Detailed description In the drawings, in which like reference characters refer to like parts thruout the several views:

Fig. 1 is a plan view of an optical sighting device adapted for mounting on an adapter at the muzzle end of a gun barrel.

Fig. 2 is a detailed sectional view in elevation taken on the line 22 of Fig. 1.

Fig. 3 is a sectional plan view adjusting means taken on the line 3-3 of Fig. 2.

Fig. 4 is an elevational view of a holder or adaptor for the device of Fig. 2, about to be inserted into a gun-barrel (shown in phantom).

Fig. 5 is an elevational view of a smaller adaptor about to be inserted into a rifle-barrel.

Fig. 6 is a schematic view of the optical elements of a breech-type predictor, with the housing and adjusting of the reticle and its 2,702,945 g Patented Max-.1, 1955 2 means therefor, and the gun-breech chamber being shown in phantom.

Fig. 7 is an end view of the vmodificationofFig. 6.

With reference now to the drawings, Figs. 1-5 disclose a preferred form of the apparatus'employed in practicing the impact-predicting method hereinafter described. This form of sighting apparatus comprises a body member generally designated as 1, WhiChlS preferablyformed by providing a block of metal witha plurality of parallel and intersecting bores into which the several elements of the device are inserted. Into meet such bores a conventional objective-lens assembly 3, having the usual lens 5, is inserted and held therein by 'threads'6 on'a reduced-diameter portion of its shell '7 -Inserted into another bore at right angles to that of the objective-lens assembly, is an eye-piece lens-assembly 9, having the usual lenses 11 and 12 and also heldin the bore by threads on a reduced portion of its shell.

To optically aline the two lens-assemblies of the device, there is placed a right isocele s prism 13, having its right-angled faces perpendicular, respectively, to the axes of said assemblies, and held firmly in such position by a bevelled push rod 15, pressed against the hypotenuse surface by a spring 16 compressed by the threaded plug 17. The prism 13 is inserted into recess '18 of the body 1 which opens thru the bottom of the body andwhich is covered by a removable plate 19. Between the prism 13 and the pushrod 15 may be inserted a protective shield 20, of soft metal or other material and preferably having a blackened upper surface. Of course, a flat mirror may be substituted for the prism 13, if desired.

Resting upon, or otherwise held parallel to, the upper face of the prism 13 is the reticle member 21, in the form of a transparent wafer of glass or the like, and having three sets of parallel faces, all perpendicular to each other, as shown in Figs. 2 and 3. One face of each lateral pair of faces is engaged by an adjustable screw 27. Opposing the action of screws 27 are two plungers 25 firmly pressed against the reticle member 21 by springs 26. The adjustment screws 27 are preferably located deep in their threaded bores to make them inaccessible for tampering or for accidental disturbance. As a further precaution, the bores may be closed by threaded plugs 29 which may be provided with small recesses in their faces (in place of the kerfs shown) whereby they may be removed only by a specially designed tit-wrench.

The rectile member 21 carries the usual cross-hairs 23, which are preferably fine lines etched in one surface of member 21 so as to lie in the focal plane of the image formed by the objective lens 5.

As shown in Fig. 2, the plug 17 fits deeply in the bore 30, which is slightly enlarged andaccurately bored at its outer end to receive the tip end 37 or 37a of any one of a plurality of adaptors 31 and 31a (Figs. 4 and 5), by which the sight body 1 may be accurately alined with the bore of guns of various calibers. Slots 41 and 41a (Fig. 2) make the portion of body 1 having the bore 30 therein constrictable about tips 37 or 37a by a tightening of screw 42. Screw 42 extends slightly into the bore 30 so as to enter depression 39 or 39a in the tips 37 and 37a of the adaptors.

The adaptors 31 and 3111 are spool-shaped, having accurately machined guide cylinders 33 and 33a which fit snugly in the bores 53 and 53a of gun or the like 51 and 51a. By the use of adaptors of various sizes, the sighting device can be used with a large number of guns or the like of different calibers. A flange or other stop member 35 or 35a may be provided at the outer end of the adaptor to prevent its being inserted too far in the barrel of the gun.

Fig. 6 is a schematic showing of a modification of the invention adapted for insertion in the breech end of a gun 61, which has the usual enlarged breech chamber 63, conically necked down to bore-diameter at 65. The breech-type bore-sighting device is generally designated as 67 and has a cylindrical body 68 beveled at 69 for centering engagement with the conical surface 65 of the gun-breech chamber 63. Toward its other or rear end, the body 68 is provided with two fixed centering or guide ribs 83, spaced approximately apart. A third rib, also about 120 from the others, is mounted for slight radial movement against the action of spring 87, for ease in placement and removal of the sighting device and to provide a slight adjustment of the device to prevent too loose or too tight fits due to slight inaccuracies in machining or due to wear, differential thermal expansion, etc.

The sighting device has the usual image-forming lenses 71 and 73 and eye-piece lens 81. A re'ticle member 75, carrying conventional cross-hairs (not shown) is mounted for vertical and horizontal adjustment in the focal plane of th image, by a pair of adjusting screws 77 (only one of which is" shown in Fig. 6). Screws 77 are shown with their heads slightly countersunk in their bores and provided with ker'fs, whereby they are not easily tampered with, but can be adjusted by a small screwdriver.

While the sighting devices of Figs. 2 and 6 are shown as being adapted for insertion of their mounting portions into the muzzle or breech end of the barrel of a gun or the like, it is to be understood that said devices can easily be adapted for attachment to any convenient portion of a gun carriage which has an invariable position relative to the axis or said barrel,

The impactepredicting sighting devices of this invention are calibrated and used as follows: The gun (or one of a series of identical guns) for which impact-predicting is desired, is sighted at a target selected at a range at which great accuracy is desired, and a test round is fired. The gun is immediately re-laid by its conventional sights on the same target. (11. desired, a series of three or more rounds may be fired to more accurately establish the center of impact.) The impact-predicting device herein described is then inserted into the breech or into the muzzle of the gun (or attached to the carriage in other manner to be fixedly alined with the axis of the barrel) and the reticle-adjusting means are adjusted so that the cross-hairs quarter the center of impact. Caps 29 are next tightly inserted to prevent accidental or tampering disadjustment of the reticle, and the predictor is then stored in a safe place with the equipment for the gun (or group of guns) for future use in predicting exact point of impact (without test rounds) for combat firing or for calibrating remounted orre'placed regular sighting apparatus.

Conventional sights are zeroed in by using the predictor to indicate the center of impact (as accurately as would costly, time-consuming and dangerous locationrevealing test-firing) and then adjusting the conventional sighting apparatusto fix on the predicted center of impact.

While I. have shown and described several preferred embodiments ofthe invention it is to be understood that various changes may be made in the size, shape, composition and/ or arrangements of the parts, and in the practice of the methods disclosed, without departing from the spirit of the invention as defined by the appended claims.

Having thus described my invention, what I claim as new and desire to secure by -Letters Patent of the United States is:

1. Amethod of predicting the center of impact of projectiles to be fired from a bored projectile-launching apparatus having conventional sighting apparatus, said method comprising: aiming said projectile-launching ap- 4 1 paratus at a target point at selected range; firing a stand ard projectile from said apparatus and noting its poin of impact; re-aiming said projectile-launching apparatus at the original target point; attaching impact-predictor sighting means having adjustable sight-line-defining means to said apparatus in such manner as to be invariably alined with the bore thereof; adjusting said sight-line-defining means of said impact-predictor sighting means to fix on the center of impact of the previously fired projectile; removing said impact-predictor-sighting means from said apparatus; and thereafter attaching said impact-predictor-sighting means to said apparatus as be fore, and sighting therewith to predict points of impact y hti g o y- 2. A method of predicting the center of impact of projectiles to be fired from a bored projectile-launching apparatus having conventional sighting apparatus, said method comprising: aiming said projectile-launching apparatus at a target point at selected range; firing a standard projectile from said apparatus and noting" its point of impact; re-aiming said projectile-launching apparatus at the original target point; attaching impact-predictor sighting means having adjustable sight-line-defining means to said apparatus in such manner as to be invariably alined with the bore thereof; adjusting said sight-linedefining means of said impact-predictor sighting means to fix on the center of impact of the previously fired projectile; removing said impact-predictor-sighting means from said apparatus; storing the same in a safe place functionally associated with said projectile-launching apparatus; and thereafter attaching said impact-predictorsighting means to said apparatus as before, and sighting therewith to predict points of impact by sighting only.

3. A method of alining the conventional sighting apparatus of a gun or the like to accurately indicate true centers of impact at pre-selected ranges, comprising: providing said gun or the like with an on-carriagemountable impact-predictor sighting means, calibrating said impact-predictor sighting means and employing the same to predict a point of impact by and according to the steps recited in claim 1, and finally alining said eonventional sighting apparatus to fix on said point of impact predicted by said impact predictor.

References Cited in the file of this patent UNITED STATES PATENTS 793,131 Henkes June 27, 1905 1,128,410 Cleary Feb. 16, 1915 1,311,349 Hoagland -1 July 29, 1919 2,018,549 Ekdahl Oct. 22, 1935 2,294,913 Kaufman et al. Sept. 8, 1942 2,353,272 Simmons et al. July 11, 19.44 2,378,545 Fraser et al. June 19, 1945 2,427,516 Unertl et al. Sept. 16, 1947 2,496,045 Ford Jan. 31, 1950 2,548,861 Brown Apr, 17, 1951 2,548,871 Cranmer Apr. 17, i

FOREIGN PATENTS 563,999 Great Britain Sept. 8, 1944 

